As this type of device, a device (so-called developing cartridge) disclosed in JP-2009-63635-A is known. This device is adapted so as to be detachably mounted on a body portion in an image forming apparatus, such as a laser printer. This device is adapted so as to supply a charged non-magnetic monocomponent developer to the surface of a photosensitive body provided within the image forming apparatus, and thereby develop an electrostatic latent image formed on the surface.
This device has therein a box-shaped casing which accommodates a non-magnetic monocomponent developer, and a developing roller which is rotatably supported by this casing. An opening is formed toward the developing roller in the casing. The developing roller includes a columnar roller body portion, and a non-magnetic monocomponent developer is carried on a columnar surface-like outer peripheral surface of the roller body portion.
Additionally, seal members (side seals) for suppressing (preventing) that a non-magnetic monocomponent developer leaks out to the outside on both ends of the roller body portion in the developing roller are fixed to the casing at positions facing the both ends. Here, in the non-magnetic monocomponent developing device, the above-described leak of a non-magnetic monocomponent developer to be used cannot be suppressed in non-contact with the developing roller by a magnetic means, such as a magnet. Thus, in the non-magnetic monocomponent developing device, the above-described seal member is provided so as to rub against both ends of the roller body portion while being elastically brought into contact therewith.